1. Field of the Invention
The present invention relates to a pressure sensor device and a suction release apparatus, and more particularly to a pressure sensor device which is provided in a pressure generating apparatus for setting the inside of a pressure tube in a negative pressure with a negative pressure-generating valve for generating the negative pressure, and setting the inside of a pressure tube to a positive pressure with a positive pressure-generating valve for generating the positive pressure, the pressure sensor device being provided for detecting the pressure inside the pressure tube.
2. Description of the Related Art
Conventionally, there is proposed a pressure generating system for suctioning work by placing the interior of a pressure tube connected to a work in a negative pressure state (a vacuum state but not a complete vacuum state). Note that the pressure generating apparatus is provided with a pressure sensor device for detecting the pressure (either positive pressure or negative pressure) inside a pressure tube and displaying the pressure detected inside the pressure tube.
In the above pressure generating system, the vacuum generating electro-magnetic valve is opened to place the interior of the pressure tube in a negative pressure state. Namely, the pressure generating system allows compressed air supplied from a compressor (on the primary side) to flow into a diffuser by opening the vacuum generating electro-magnetic valve. Along with this, the interior of the pressure tube is placed in a negative pressure state by cawing the air in the pressure tube (on the secondary side) to flow into the diffuser.
Further, in this pressure generating system, in order to place the interior of the pressure tube in a positive pressure state, the vacuum generating electro-magnetic valve is closed and a vacuum release electro-magnetic valve is opened. Namely, in this pressure generating system, by closing the vacuum generating electro-magnetic valve and opening the vacuum release electro-magnetic valve, compressed air supplied from the compressor (primary side) can be prevented from flowing into the diffuser and can be made to flow into the pressure tube, thereby placing the interior of the pressure tube in a positive pressure state. Note that the term "breakdown" is used because compressed air is made to flow into the interior of the pressure tube thereby breaking down the state of vacuum which had existed in the pressure tube.
However, a sequencer located outside the pressure generating apparatus directly controls the vacuum generating electro-magnetic valve and the vacuum release electro-magnetic valve with the result that a control load of the sequencer is large. In particular, when various types of control have to be performed on the vacuum generating electro-magnetic valve and the vacuum release electro-magnetic valve because of the type of work (the weight and the state of the suction surface), because the sequencer has to perform each of the controls, the control load becomes increasingly larger.
Furthermore, when the pressure sensor device detects the pressure in the pressure tube and the detected positive pressure is a threshold value or greater, a positive pressure state signal is output via a first signal line. On the other hand, when the detected negative pressure is a threshold value or greater, the negative pressure state signal is output via a second signal line. In other words, two signal lines are required to output the pressure (positive pressure and negative pressure) state in the pressure tube.